First Alert CO5120PDBN Hardwired Carbon Monoxide Alarm with Battery Backup and Digital Display 120-volt hardwired carbon monoxide alarm wires directly into your home's electrical system Electrochemical sensor and microprocessor accurately detect carbon monoxide while minimizing false alarms Backlit digital display allows you to view current and peak levels Easy-to-access battery drawer; 9-volt battery included Carbon monoxide detector can integrate with up to 18 compatible devices for extended coverage Superior carbon monoxide sensor with battery backup Inter-connectable with BRK and First Alert hardwired smoke and carbon monoxide alarms Microprocessor controlled for fewer nuisance alarms Simple to use silence/test button; convenient alarm latch indicator 9-volt battery included; 7-year limited warranty